As cellphone networks get faster, it’s getting a lot easier to hit your data cap without realizing it – and that can result in some nasty overage charges. Onavo is an app that can let you know as you approach that limit.

In a nutshell, the app runs everything you do online through its servers. It will condense the results, which cuts back on your usage. At the same time, it will keep a running tally of the bandwidth you’ve used, letting you know when you get close to your limit.